The present invention is related to a wind farm with plural wind turbines, and a method for regulating an electric variable fed into an electricity supply mains by a wind farm having plural energy turbines.
There is an increasing demand by the companies which operate electricity supply mains that wind farms actively contribute to the regulation of the grid voltage. Demands concerning the promptness of the regulation are also made in this, which necessitate additional measures for the promptness of the regulation, in particular in wind farms with wind turbines that are spatially positioned far away from each other.
From DE 10 2004 0 60 943 A 1, the entire contents of which is incorporated herein by reference, a wind farm power regulation is known, in which a farm master is provided for the control of the wind turbines. The farm master has a power regulator, which is realised with multiple circuits, wherein one of the circuits for power regulation is realised as a fast closed loop, which presets the power output for a first group of the wind turbines. A second circuit, which acts on a second group of the wind turbines, is realised as a slow closed loop. The repartition of the wind turbines into two groups has the effect that a first group can quickly react to changes and disturbances of the desired value, whereas the steady state accuracy is achieved by way of the slowly regulated second group of wind turbines.
From an article “A novel centralised wind farm controller utilising voltage control capability of wind turbines” by Jens Fortmann et al., the entire contents of which is incorporated herein by reference, which was published for the 16th Power Systems Computation Conference in July 2008 in Glasgow, a cascade regulation of wind turbines in a wind farm is known. In this, a fast continuous voltage regulation on the level of the wind turbines is combined with a relatively slow desired value regulation on the wind farm level. Desired voltage values for the control of the wind turbine are set on the wind farm level. The desired voltage value for the wind turbine is compared with the measured actual value in the wind turbine, and the difference is supplied to a voltage regulator as the control deviation. The regulator on the wind farm level is realised as a slow regulator in this, in order to avoid undesired regulation interventions. In this regulation approach for the wind farm, the regulator arranged on the farm level outputs its manipulated variable as an input variable to a voltage regulator in the wind turbine.
From EP 1 512 869 A1, the entire contents of which is incorporated herein by reference, a voltage regulation for a wind farm is known in which a voltage regulator on the farm level determines a desired value for a reactive power to be manipulated, which is applied to a turbine control of the individual wind turbines. The turbine regulates the reactive power which it generates to this preset desired value. The regulator on the turbine level is realised as a fast regulator, whereas the regulator on farm level is realised as a slow regulator. A cascaded arrangement of the regulators is selected even in this, because the slow regulator on the farm level applies its manipulated variable as a desired value to the fast regulator on the turbine level.
As is commonly known from control engineering, using a cascaded regulator structure is accompanied by less flexibility in the layout of the regulators.
The present invention is based on the objective to provide a wind farm and a method for controlling a wind farm, which permits a fast regulation by the individual wind turbines with simple means, but also permits a sufficiently high flexibility of the layout of the regulators and a fast regulator intervention even at wind turbines that are positioned far apart from each other.